The ultimate goal in galaxy studies is having a complete picture of galaxy formation and evolution across the history of the Universe. A robust determination of the abundance of massive (an even quiescent) galaxies at high redshift is essential to constrain current models of galaxy formation and alleviate the tension between existing models and observations.
In this context, this Ph.D. Thesis addresses the challenge of studying the build-up of massive galaxies adding a new population of optically faint Balmer Break Galaxies (BBGs), which are bright at longer wavelengths, to the general population of massive galaxies at z > 3.
